This animal study (n=8) investigated the efficacy of Banisteriopsis caapi (0.1 – 0.3 mg/kg harmine) alone and in combination with L‐DOPA (4 – 7 mg/kg) to treat parkinsonian dyskinesia in a marmoset disease model. B. caapi alone has a mild antiparkinsonian effect but does not enhance the L‐DOPA response or reduce dyskinesia.
Abstract
“Introduction: Banisteriopsis caapi (B. caapi) contains harmine, harmaline, and tetrahydroharmine, has monoamine oxidase inhibitory activity, and has reported antiparkinsonian activity in humans when imbibed as a tea; however, its effects are poorly documented.
Methods: For this reason, motor function was assessed in 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine‐treated common marmosets following administration of B. caapi extract (28.4–113.6 mg/kg; po), harmine (0.1 and 0.3 mg/kg; sc), and selegiline (10 mg/kg; sc), alone or with a submaximal dose of L‐3,4‐dihydroxyphenylalanine (L‐DOPA; 4–7 mg/kg).
Results: L‐DOPA reversed motor disability, increased locomotor activity, and induced moderate dyskinesia. B. caapi did not increase locomotor activity or induce dyskinesia but at 56.8 and 113.6 mg/kg improved motor disability. The L‐DOPA response was unaltered by co‐administration of B. caapi. Harmine (0.1 and 0.3 mg/kg) produced a mild improvement in motor disability without affecting locomotor activity or dyskinesia but had no effect on the L‐DOPA‐induced antiparkinsonian response. Selegiline (10 mg/kg) alone improved motor function to the same extent as L‐DOPA, but with only mild dyskinesia, and did not alter the response to L‐DOPA, although dyskinesia was reduced.
Discussion: The findings suggest that B. caapi alone has a mild antiparkinsonian effect but does not enhance the L‐DOPA response or reduce dyskinesia.”
Authors: Ria Fisher, Louise Lincoln, Michael J. Jackson, Vincenzo Abbate, Peter Jenner, Robert Hider, Andrew Lees & Sarah Rose
Summary
1 | INTRODUCTION
Parkinson’s disease is a progressive neurodegenerative disease that affects motor function. LDOPA is the most widely used and efficacious symptomatic treatment, but chronic use can lead to unwanted involuntary movements.
Banisteriopsis caapi is a liana found in the Amazon basin that contains a number of carbolines that have been shown to have MAO inhibitory properties. It is thought that these effects are mediated through its constituent karbolines.
Harmine increased dopamine levels in the striatum of rats and rabbits, supporting the idea that MAO inhibition underlies the antiparkinsonian activity observed.
This study used a marmoset model of PD to evaluate the effects of B. caapi extracts and one of its constituent carbolines, harmine, on motor dysfunction.
2.1 | Preparation of extract of B. caapi
Dried whole stem of B. caapi was obtained from Dr. Marcos Serrano Duenas, Neurology Service, Carlos Andrade Marin Hospital Quito, and an extract was prepared as previously described. The extract was analysed for levels of harmine, harmaline, and tetrahydroharmine.
2.2 | HPLC analysis
A HP1050 HPLC system was used to analyse the samples. A linear gradient of mobile phase B over mobile phase A was employed, and the eluents were monitored at wavelengths between 210 and 280 nm.
2.3 | Animals
All studies were performed in the same group of previously MPTPtreated common marmosets (Callithix jaccus; aged 3-10 years), and received meals of fresh fruit, cereals, and protein twice daily.
Animals were treated with MPTP between 1 and 4 years prior to the start of the study. They became bradykinetic and rigid, but were able to eat, drink, and move around the home cage unaided.
All experiments were performed according to the Animals (Scientific Procedures Act) 1986 and local ethical approval was obtained. Animals received a drug washout period of at least 4 weeks prior to the start of this study.
2.4 | Treatments
Benserazide prevents the peripheral conversion of LDOPA to dopamine and was dissolved in 10% sucrose and used as the vehicle for dissolving LDOPA methyl ester (ME). LDOPAME was dosed concomitantly with benserazide.
B. caapi stem extract contained 35.2 mg/g harmine, 17.6 mg/g tetrahydroharmine, and no harmaline. The extract was administered by oral gavage at a dose volume of 2 ml/kg.
2.5 | Administration of B. caapi extract
Animals were treated with B. caapi extract and LDOPA in combination with a submaximal dose of B. caapi extract or vehicle. The animals drank the concentrated tea with no adverse effect.
B. caapi extract was administered immediately prior to LDOPA (7 mg/kg, po) or vehicle at t = 0 hr.
2.6 | Administration of harmine
Animals were treated with harmine, L DOPA, and vehicle. The drugs were administered in a randomized manner with at least 2 days between each treatment.
2.7 | Administration of selegiline
Selegiline (10 mg/kg, sc) was administered to rats to block LDOPA (4 mg/kg, po)induced motor activity.
2.8 | Behavioural assessment
On test days, animals were placed into automated test units and were assessed for basal locomotor activity, motor disability, and dyskinesia.
2.9 | Locomotor activity
Each automated test unit was fitted with a clear Perspex door and eight horizontally orientated photoelectric emitters/detectors to permit optimal assessment of activity.
HPLC analysis of Banisteriopsis caapi dried whole stem extract for tetrahydroharmine, harmine, and harmaline showed that the extract contained high levels of these alkaloids.
2.10 | Motor disability
Motor disability was assessed before and after drug treatment for 5 hr using an established motor disability rating scale. A maximum score of 18 indicated severe motor disability, a minimum score of 0 indicating maximum reversal of motor disability.
2.12 | Data and statistical analysis
Data were presented as median in time course and area under curve (AUC) for locomotor activity, reversal of motor disability, and dyskinesia expression. ANOVA and Newman-Keuls tests were used for statistical analysis.
3.1 | The effect of B. caapi alone and combined with L‐DOPA (7 mg/kg, po) on locomotor activity, motor disability, and dyskinesia
No one aspect of motor disability was specifically affected by B. caapi treatment, but at all doses investigated, B. caapi did not affect locomotor activity or induce dyskinesia.
3.2 | The effect of treatment with harmine alone and in combination with L‐DOPA (4 mg/kg, po) on locomotor activity, motor disability, and dyskinesia
LDOPA and harmine reversed motor disability, increased locomotor activity, and expressed mild to severe dyskinesia, but harmine alone had no effect on locomotor activity.
LDOPA (4 mg/kg, po)induced reversal of motor disability or increase in locomotor activity was not altered by harmine (0.1 and 0.3 mg/kg sc), although the severity of the dyskinesia was increased by harmine.
3.3 | The effect of treatment with selegiline alone and in combination with L‐DOPA (4 mg/kg, po) on locomotor activity, motor disability, and dyskinesia
Selegiline alone produced a similar reversal of motor disability and increase in locomotor activity as the submaximal dose of LDOPA (4 mg/kg, po), although with a reduced peak effect.
4 | DISCUSSION
Previous studies suggest that B. caapi extracts may possess antiparkinsonian activity based on limited clinical experience in humans. However, alternative mechanisms have been proposed, including the monoamine oxidase inhibitory actions of the carboline content of these extracts. We examined the effects of B. caapi extracts on motor function in the most predictive primate model of drug effect in PD, and compared them with harmine and selegiline.
MPTPtreated monkeys are highly responsive to LDOPA treatment, and the drug reverses bradykinesia and normalizes motor function. B. caapi extract produced some reversal of motor disability in PD animals, but not to the same extent as LDOPA (7 mg/kg, po). When combined with LDOPA, the effects of B. caapi extract were not additive, and suggest that B. caapi may be relevant to early monotherapy in PD. The dose of B. caapi extract used in this study was clinically relevant and resulted in a significant improvement in motor function in patients with PD.
The modest effects seen with B. caapi extracts may be due to the monoamine oxidase inhibitory actions of the constituent carbolines, but the level of harmine in the tea was surprising as previously it had been reported that harmaline was present.
Harmine, a major carbamoline component of B. caapi, was shown to reverse motor disability in rats without increasing locomotor activity or dyskinesia. This suggests that harmine may be a MAOI-based effector.
Harmine, a MAO inhibitor, improved motor disability in PD patients, but the effect was not obvious when harmine was combined with a submaximal dose of LDOPA. However, it would depend on the extent to which harmine blocked MAO activity in the brain.
To assess whether B. caapi extracts or harmine inhibit MAOB activity, we compared the effects of B. caapi extracts and harmine to those of selegiline, a selective MAOB inhibitor used in PD. Selegiline reversed motor disability and increased locomotor activity with little or no expression of dyskinesia. Although selegiline did not potentiate the effects of LDOPA in B. caapi and harmine, it increased the duration of response and reduced the expression of dyskinesia, which is unexpected as it does not reflect the clinically accepted effect of selegiline in enhancing dopamine’s effect in humans. We could find no prior investigation of the symptomatic effects of selegiline in MPTPtreated primates.
Evidence suggests that harmine, a constituent of B. caapi, is neuroprotective, antiinflammatory, and antiapoptotic, and could be beneficial in the chronic treatment of PD.